The present invention relates to a controller for a molding machine, more precisely relates to a controller for a molding machine, which is capable of controlling speed of a movable section of a resin-pressurizing mechanism of the molding machine and resin pressure.
In an injection molding machine, for example, shapes of products, types of resin, types of molds, etc. have been more complex and precise, so that speed of an injection screw and injection pressure (resin pressure) must be controlled in multiple stages. To execute multistage control, conventional injection molding machines have controllers to which the speed of the injection screw and the resin pressure for each stage are inputted. Conventional control patterns are shown in FIG. 3.
in conventional control patterns of the injection molding machine, there are a speed-control area A, in which the speed of the injection screw is mainly controlled, and a pressure-control area B, in which injection pressure is mainly controlled (see FIG. 3). The speed-control area A is between an initial position IP and a predetermined position C, which is called "V-P switching position". In the speed-control area A, the speed of the injection screw with respect to its position on the stroke is controlled in multiple stages; the injection pressure is not precisely controlled. When the injection screw reaches the V-P switching position, the control area is changed from the speed-control area A to the pressure-control area B. In the pressure-control area B, the injection pressure with respect to time is controlled in multiple stages; the speed of the injection screw is not precisely controlled.
However, the conventional controller has the following disadvantages.
Firstly, in case of complex molding in which various conditions, such as shapes of products, molding materials, types of molds, it is difficult to control molding machines in the speed-control area and the pressure-control area separately. For example, there are cases, in which multistage control of the injection pressure is required in the speed-control area, and vice versa. In these cases, if the speed and the pressure are separately controlled in the control areas, it is difficult to mold desired products.
Secondly, to separately input control data (speed and pressure) in the speed-control area and the pressure-control area, the V-P switching position must be defined. But it is difficult for inexperienced operators to define a proper V-P switching position. It is further difficult to define the control data according to the V-P switching position.